Happy? Sad? Breastfeeding May Affect Babies' Awareness of Social Cues

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Breastfeeding might affect the way babies with a certain genetic
makeup perceive other people's emotions, according to a new
study.

In the study, researchers looked at the relationship between
being breastfed and perceiving emotions in 49 female and 49 male
7-month-old infants. The babies were shown photos of faces whose
eyes expressed emotions including happiness or anger, and the
researchers measured
how long the babies looked at them.

The researchers found that among the 44 babies in the study who
had a certain genotype of the gene CD38, called the CC genotype,
those who had been exclusively breastfed for the longest time
tended to look longer at happy eyes, and for less time at angry
eyes, compared with infants who had been
exclusively breastfed for a shorter time.

The results show that these breastfed infants seemed to be more
sensitive to the social cues expressed in people's eyes, the
researchers said.

One important cultural aspect of the study was that it was
conducted in Germany, and not in the United States. Most mothers
there are entitled to a one-year-long paid maternity leave,
making it easier for moms to breastfeed
if they choose to, said study author Tobias Grossmann of the
University of Virginia in Charlottesville. Almost all of the
mothers in the study were still on maternity leave when the study
was conducted, he said.

The goal of the new research is not to put pressure on mothers to
breastfeed their children, but rather to examine potential
biological mechanisms connected to breastfeeding and babies'
social behaviors, Grossman stressed. "It is very important not to
put any stigma on what mothers do," he noted. [ 7
Baby Myths Debunked ]

For the babies in the study who didn't have this CC genotype, the
length of time they were breastfed was not linked with how long
they looked at the emotional faces, according to the study.

The link seen in the study appears to involve oxytocin,
a hormone associated with social bonding. Previous research
on humans has shown that the changes in the CD38 gene may be
associated with lower levels of oxytocin in the brain, and that
people with these changes may have impaired social skills, the
researchers said.

The new results suggest that, through acting as an external
source of oxytocin, breastfeeding may help to regulate the
oxytocin levels in the infants with this genotype and improve
their social skills, the researchers said.

The specific genotype in the babies in this study has also been
linked to an increased risk of autism, the researchers said. The
new findings suggest that the "breastfeeding experience enhances
prosocial tendencies in infants that are genetically at risk for
autism," they wrote in the study.

It is not clear whether this
effect of breastfeeding may disappear once the babies are
weaned, or whether it persists and eventually affects the way the
children behave later in life, Grossmann said. The researchers
are currently carrying out a larger project to investigate this
question, he said.

The new study was published today (Sept. 14) in the journal
Proceedings of the National Academy of Sciences.